A warehouse that has such a structure, in place of the bulky and energy-intensive conventional translation-lifting devices of the Cartesian type, has more compact movement means, generally comprising a first primary means (referred to as a “shuttle”), and a second auxiliary means (referred to as a “satellite”), operatively connected to the first primary means.
The shuttle moves along a main aisle, defined at the sides thereof by the warehouse shelves, which shelves provide a plurality of stations, along secondary aisles, where the cargo units can be housed. Once the shuttle has reached the secondary aisle at which the station where a load has to be deposited or withdrawn is located, the satellite disconnects from the shuttle, which satellite, moving along the secondary aisle, materially carries out the unit unloading or withdrawing operation. The shuttle, during the above-mentioned operation, remains stationary, waiting for the satellite to come back.
The automated storage system just described suffers from two kinds of problems, related to the precision of the displacements of the shuttle and the satellite, as well as the optimization of the operative times.
A first problem relates to the accuracy with which the proper positioning of the movement means within the warehouse can be controlled. Current position feedback systems, generally based on encoder transducers, suffer from errors due to stacking up of the shelving constructive tolerances, the latter increasing more and more as the warehouse dimensions increase.
Wear is another factor contributing to decrease the reliability of the current solutions for controlling the positioning. For example, an encoder detecting the rotation of vehicle wheels, converting the number of recorded rotation in a linear length, suffers from the same wheel wear, since the conversion algorithm continues to operate based on values that do not correspond to the real ones. Vibrations or slips of the wheels may also affect the correctness of the assessment of the handling vehicles positioning.
A second problem relates to the downtimes the various handling operations. Downtimes are due to the fact that the shuttle, before moving again, has to wait for the completion of the withdrawal or deposition operation of the load by the satellite.